520 ppb to ppm

520 ppb = 0.52 ppm

ppbppm
505 ppb0.505
510 ppb0.51
515 ppb0.515
5200.52
525 ppb0.525
530 ppb0.53
535 ppb0.535

520 ppb = 0.52 ppm

Formula

1 ppm = 1 mg/L (aqueous, density ≈ 1 kg/L) · 1 ppb = 0.001 mg/L · 1% = 10,000 ppm